President Clinton's former top aide said yesterday that "obviously there was something more here" than the president has disclosed regarding his relationship with Monica S. Lewinsky and called on Clinton to come forward and explain it to the American public.

Leon E. Panetta, who served as White House chief of staff until January 1997, said he accepts Clinton's assertion that he never had sexual relations with Lewinsky and never told her to lie under oath. But Panetta added that it is increasingly clear that Clinton had some sort of relationship with Lewinsky.

"I take him at his word and I think the American people take him at his word. They're willing to give him the benefit of the doubt," Panetta said on ABC's "This Week." "But I also think that at some point he's got to tell the American people the truth of what was behind this relationship. Obviously, there was something more here. And it's got to be explained to the American people."

Panetta's comments are the latest from Clinton's own circle suggesting he has not been fully candid with the public about Lewinsky and hinting at considerable doubt among those who have been closest to him. Shortly after the Lewinsky story broke, Panetta suggested the possibility of resignation, if the allegations were true. Former White House aides George Stephanopoulos and Dee Dee Myers likewise have made skeptical statements. And even current White House press secretary Michael McCurry has publicly pondered the ramifications if Clinton is lying.

Moments after Panetta's appearance, Stephanopoulos, now an ABC commentator, echoed his sentiment, citing the three dozen times Lewinsky returned to the White House after leaving her low-level job there in April 1996. "It's pretty clear that there was some relationship here," Stephanopoulos said. "It's not normal to have that many visits with an intern."

The White House declined to respond formally to Panetta's statement yesterday, but aides made clear that they were unhappy with it. From their point of view, anything that focuses attention back on Clinton's behavior rather than the conduct of independent counsel Kenneth W. Starr is unwelcome.

The degree to which the White House has been successful in shifting attention to Starr was evident yesterday when one of the prosecutor's leading Republican defenders said someone else should have been chosen to look into the Lewinsky matter.

Sen. Arlen Specter (R-Pa.), a member of the Senate Judiciary Committee, said Starr could not be seen as neutral because of his long history of investigations into Whitewater and other matters connected to the Clinton White House. Instead, Specter said, Attorney General Janet Reno should have asked for a new independent counsel to investigate whether Clinton tried to obstruct justice in the Paula Jones case by urging Lewinsky to lie under oath about having had an affair.

"In the context where Starr has been in this matter for so long, and many people think he's out to get the president, and you have this adverse public reaction to Starr, I think it would have been much wiser had someone other than Starr run this phase of the investigation," Specter said on "Fox News Sunday."

Until now, Republicans have steadfastly defended Starr's actions, but Specter's comments indicated that at least some GOP leaders have begun to conclude that he has become too much of a lightning rod. If Starr is seen as too partisan, as polls indicate, then it will be harder for Congress to pursue impeachment proceedings based on his investigation.

Starr became involved in the Lewinsky case after he was approached by her friend, Linda R. Tripp, with tape recordings of conversations Tripp had with Lewinsky about the president. Starr's office then put a hidden microphone on Tripp, who met again with Lewinsky and got her to repeat her assertions that she had a sexual relationship for a year and a half with Clinton and that he urged her to deny it to Jones's lawyers. Starr took his information to Reno and both she and a panel of judges agreed to expand his authority to investigate possible obstruction of justice and subornation of perjury.

Still, Specter, a former prosecutor who has spoken with Starr since the crisis erupted, said the independent counsel's tactics have not gone overboard. "Starr was right," he said. "He went right up to the line. He hasn't crossed the line for prosecutorial action, but he's gone right up to the line."

In a separate development, Lewinsky's lawyer disputed reports that she discussed her relationship with Clinton in electronic messages to Tripp that have been turned over to Starr. According to copies of e-mail obtained by Newsweek, Lewinsky complained that "Big Creep didn't even try to call me on V-Day" last year after she placed a Valentine's Day personal ad in The Washington Post.

"I'd like to cross-examine Linda Tripp on just how she happened to have hard copies of e-mail and who in fact really did create that e-mail," Lewinsky's attorney, William H. Ginsburg, said on CNN's "Late Edition." "I doubt very much that it was Monica Lewinsky."